mineral

Orthoclase Feldspar with Quartz

Orthoclase (KAlSi3O8)

Hardness: 6 (Mohs); Color: Salmon pink to flesh-red; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Two directions at 90 degrees; Specific Gravity: 2.55-2.63.

Hardness: 6 (Mohs)
Color: Salmon pink to flesh-red
Luster: Vitreous to pearly

Identified May 16, 2026More mineral →

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Physical properties

Hardness: 6 (Mohs); Color: Salmon pink to flesh-red; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Two directions at 90 degrees; Specific Gravity: 2.55-2.63.

Formation & geological history

Formed primarily in plutonic igneous rocks like granite and pegmatites through the cooling of silica-rich magma; also found in metamorphic rocks like gneiss.

Uses & applications

Used in the manufacture of glass, ceramics, pottery, and as a filler in paints and plastics. Occasionally used as a semi-precious gemstone (Moonstone is a variety).

Geological facts

Orthoclase is one of the most common minerals in the Earth's crust. It is a defining mineral for the number 6 spot on the Mohs scale of mineral hardness.

Field identification & locations

Identify in the field by its salmon-pink color, blocky cleavage patterns at right angles, and inability to be scratched by a steel knife but can scratch glass. Common in mountainous regions with granitic bedrock.

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

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Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

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Epidote

Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

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